title: Cephalometric superimpositions.
abstract: OBJECTIVE
  To test the hypothesis that there is no difference between the information produced by superimposition of serial lateral headfilms on anatomical structures and that produced by superimposition on metallic implants according to the protocols of Björk.
  
  
  METHODS
  Serial cephalograms of 10 untreated subjects who had tantalum implants placed in the maxilla and mandible during childhood were analyzed. Headfilms taken at six consecutive stages of cervical vertebral maturation (CS1-CS6) for six female and four male subjects were used. Tracings were superimposed according to the methods of superimpositions advocated by the American Board of Orthodontics (ABO). In addition, superimpositions along the inferior border of the mandible were performed. Finally, superimpositions of serial tracings on stable intraosseous implants were made to determine the actual growth and remodeling patterns of the maxilla and mandible.
  
  
  RESULTS
  The ABO maxillary superimposition method underestimates the vertical displacement and overestimates the forward movement of maxillary landmarks. Superimposing on the internal cortical outline of the symphysis and the inferior alveolar nerve canals generally approximates the mandibular superimposition on implants, although the lower anterior border of the symphysis may be a preferable area of superimposition. Superimposition on the lower border of the mandible does not reflect accurately the actual pattern of growth and remodeling of the mandible.
  
  
  CONCLUSIONS
  When analyzing serial headfilms, erroneous information concerning patterns of bone growth and remodeling can be obtained if convenient, but biologically incorrect superimposition protocols are used. In addition, tooth movements measured can be distorted significantly depending on the method of superimposition.
authors.affiliation: Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, 100081 China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Gu
authors.forename: James A
authors.initials: JA
authors.lastname: McNamara
mesh_terms: D000365:Age Determination by Skeleton; D001846:Bone Development / Q000502:physiology; D016723:Bone Remodeling / Q000502:physiology; D002508:Cephalometry / Q000379:methods*; D002574:Cervical Vertebrae / Q000254:growth & development; D002648:Child; D002680:Chin / Q000033:anatomy & histology; D003764:Dental Materials; D005147:Facial Bones / Q000033:anatomy & histology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008334:Mandible / Q000033:anatomy & histology / Q000254:growth & development; D008335:Mandibular Condyle / Q000033:anatomy & histology; D008437:Maxilla / Q000033:anatomy & histology / Q000254:growth & development; D009295:Nasal Bone / Q000033:anatomy & histology; D010159:Palate / Q000033:anatomy & histology; D019736:Prostheses and Implants; D012886:Skull / Q000033:anatomy & histology*; D013635:Tantalum
chemical_list: D003764:Dental Materials; D013635:Tantalum